Stars and Constellations Stars and Constellations There are some 6,000 stars visible to the naked eye. Most of these stars can only be seen from locations far from the bright lights of a city or town. If you really want to see the stars, you either have to go to Hollywood or get out of Dodge. Star Names Some of the brighter stars have proper names, but most don’t – there are just too many to give each one a name. Instead, astronomers have devised a system that assigns names to naked-eye stars based on their brightness and the name of the constellation they belong to. Following a centuries-long tradition, the brightest star in a constellation is designated by the first letter of the Greek alphabet, Alpha, followed by the genitive form of the Latin name of its constellation. For example, the brightest star in the constellation Orion is called Alpha Orionis. It also has a proper name: Rigel. (We’ll talk more about constellations later. Right now we’re going to focus on individual stars.) When the letters run out, stars are identified by various alphanumeric designations. A funny thing about Rigel: even though it’s the brightest star in Orion, its designation is Beta Orionis.

Astronomers originally thought that Betelgeuse, another star in Orion, was a little bit brighter, but improvements in photometers in the 20th century revealed that Rigel is actually the brighter star (it’s possible that Betelgeuse might have been brighter in the past, when astronomers first began to designate stars with Greek letters). Bright Stars and Dim Stars Long before the invention of the telescope, astronomers also came up with a numerical system for classifying stars by their brightness. They decided that the brightest stars would be called First Magnitude. Those half as bright as First would be called Second Magnitude, then Third Magnitude, and so on down to Sixth Magnitude, which denotes the dimmest stars visible to the naked eye. We use a modified form of this system today. The brightest star in the nighttime sky is called Sirius. It’s in the constellation Canis Major, the Big Dog, and it’s sometimes called the Dog Star. Its magnitude is minus 1.4, which we write as –1.4. This may seem a little confusing, but it isn’t that hard to understand. A couple of centuries ago, astronomers decided to make the magnitude scale more precise.

They knew the Sun and Moon and some of the planets are brighter than the brightest stars, so these were given negative magnitudes. They also realized that a First Magnitude star is actually a bit more than twice as bright as a Second. In order to keep Sixth Magnitude as the faintest star visible to the naked eye, astronomers recalibrated the magnitude system to follow a logarithmic scale . Each stellar magnitude is about 2.5 times brighter than the next lower magnitude so that the difference of five magnitudes is a brightness factor of (exactly) 100. With a telescope, you can see stars much dimmer than Sixth Magnitude. TheSkyX database includes stars down to about 14th Magnitude. On a clear, moonless night, people who live in cities or suburbs can rarely see stars dimmer than Third Magnitude. If you’re just starting to learn the names of the brighter stars and constellations, you should set the magnitude filter in TheSkyX to Second or Third magnitude.

That way, when you go out at night to compare what you see on your computer to what you can see in the real sky, you won’t be confused by a screen display that shows more stars than you can actually see from your location. Setting the Magnitude Limit This command tells TheSkyX to only display stars, galaxies, clusters, or any other object type, or combination of object types, that has magnitude information, that are brighter or fainter than a selected magnitude. Controls for editing the magnitude limits are found on the Chart Elements window on the Display menu. The following example demonstrates how to change the magnitude limits for all celestial objects. 1. Make sure the Chart Elements window is visible. If it’s not, select the Chart Elements command from the Display menu to show it. 2. Highlight the Celestial Objects text by clicking on it. This selects the 40 chart elements in the Chart Elements node. 3. Click the Edit Attributes button. 4. Near the bottom of the Chart Elements window you’ll see a tab labeled Magnitude Limits. You can enter a value between 30.0 and –6.0, or change the magnitude using the sliders. Figure 71: Magnitude Limits tab on the Chart Elements window.

The attributes of chart elements (including lower and upper magnitude, angular size, font properties and colors) can be changed individually or as a group based on the items that are selected in the Chart Elements list. Number of Selected Chart Elements (Selected) This text shows the name of the selected chart element or the number of selected chart elements in the Chart Element list. Show Only Brighter Stars (Hide fainter than) Specify the magnitude of the faintest objects to be displayed on the Sky Chart. For example, if you live in a light polluted city and want to approximate the stars you can see on typical night’s sky, enter magnitude 1 or 2. Show Only Fainter Stars (Hide brighter than) The Hide Brighter Than controls provide additional filtering, displaying objects only within a specified brightness range. Larger magnitude values represent dimmer objects. The brightest objects have negative magnitudes. As you move the slider the number of stars on the Sky Chart changes to reflect the changing magnitude limits. Like land maps, star charts can be overlaid with a variety of lines and markings intended to highlight specific celestial features and help you find objects at specific coordinates.

The Chart Elements menu lets you display or hide various reference lines and symbols, but you should be aware that even though the cosmos mostly consists of empty space, a star chart can get very crowded very quickly. The celestial equator and lines of right ascension and declination can be added to the Sky Chart, for example. Experiment with this feature by clicking on the box next to a listed chart element to see how it affects the display. A Star to Guide You For people living in the northern hemisphere, probably the most noteworthy star is Polaris, the North Star. It always stays in the same part of the sky, every night, 365 days a year. The reason for this is fairly simple: Polaris happens to be located almost directly above our North Pole. As the Earth rotates on its axis, other stars rise and set, but because Polaris is right above the pole, it always seems to stay in the same place. How high Polaris is above your horizon is a direct way to find your latitude. If Polaris is 40 degrees above the local horizon, for example, you must be somewhere on the 40th latitude line.

Philadelphia and Denver are both very close this latitude, as are Naples, Italy and Beijing, China. The stars you can see on any given date and (local) time are essentially the same for all of these cities, and any other place along this line of latitude. More than anything else, latitude determines what you can see in the sky. The North Star is not visible from the Southern Hemisphere, as are most of the stars and constellations near it. And there are all sorts of stars and constellations visible from the Southern Hemisphere that we never get to see in the North (the Moon and planets are visible from both hemispheres). TheSkyX can show you what the sky would look like from any place in either hemisphere. Double Stars A little more than half of all stars actually travel in pairs, orbiting each other in space. The American astronomer Henrietta Leavitt once quipped that three stars out of every two are double. Most of them appear as single stars to the naked eye. You need good binoculars or a small telescope to resolve them as double stars (there are also triple stars and groups consisting of four or even more stars).

Some double stars are true binaries , meaning they are gravitationally bound to each other and orbit a common point in space. Others only appear to be double because they happen to lie along the same line of sight from Earth, but are in fact many light years apart and not tied to each other by gravity. One of the best-known double stars in the sky is called Mizar. It’s located in the handle of the Big Dipper. Mizar is visible only from the Northern Hemisphere, and is easiest to find in the evening sky in Spring. Select the Find tab from the vertical tabs on the left side of TheSkyX’s window. Type Mizar into the Search For text input, then click the Find button. A double red “bull’s eye” will encircle the star in the Sky Chart. The Big Dipper is one of the northern sky’s most recognizable asterisms (this term is described below). Being able to find it will help you find other nearby constellations, such as Cassiopeia. Once you’ve mastered these constellations, others will be easier to learn. Another good thing about being able to find the Big Dipper: it will make it easy for you to find Polaris, and therefore true north.

The two stars at the end of the cup of the dipper point to Polaris. Imagine a line connecting these two stars. Extend it in the direction the cup is pouring, about five times the distance between the two stars. The star you see at the end of that line is Polaris. Variable Stars Fortunately for us, and everything else that lives on Earth, the Sun radiates energy at a very nearly constant rate. But there are some stars that change in brightness dramatically over the course of a few months, and in some cases, just a few days or even hours. These are called variable stars , and TheSkyX distinguishes them with a small red “v” to the lower left of the star. The most notorious variable star is called Algol, a name derived from an Arabic word that means demon. Located in the constellation Perseus, its rhythmic dips in magnitude can easily be observed with the naked eye. Every 2.867 days, over the course of just a few hours, Algol falls from second magnitude (2.1) to third (3.4) and back. During these periodic dimmings, you can gauge its changing brightness by comparing it to other nearby stars.

The evening sky in Autumn is the easiest time to find this fascinating object (it is only visible from the Northern Hemisphere). It may have been considered demonic in ancient times, but today we know this innocent star has a companion that orbits it every 2.867 days. Algol dims when that companion passes in front of it from our perspective. Such stars make up a special class called eclipsing binaries . Constellations: Andromeda, Cassiopeia and Perseus Constellations: Andromeda, Cassiopeia and Perseus Andromeda Andromeda is a bright constellation, visible all year round in the northern hemisphere (circumpolar.) and represents the figure of a woman with arms outstretched. It contains the famous spiral galaxy M31, known as the Andromeda Galaxy. On the limit of visibility, at magnitude 4.4, it is the most distant object that can be seen with the unaided eye, and is the nearest galaxy to our own. It can be seen as a misty patch, given good seeing and a very dark background sky, free of light pollution.

The Andromeda Galaxy has two companions: M110 ( NGC 205) and M32. M110 is located one degree north west of M31 and M32 can be found half a degree south of M31. Both are elliptical galaxies. Almach, gamma Andromedae, is a beautiful double star. Even small telescopes can easily divide it's two components of mags. 2.2 and 4.8. Their beautiful contrasting colours of yellow and blue make this one of the showpiece doubles of the sky. NGC752 is a large, scatterd wide field cluster of about 60 stars of 9th and 10th mags. NGC7662 is one of the easiest planetary nebulae to see with small telescopes. Under high magnification it appears as a fuzzy blue-green disk with an elliptical outline. Cassiopeia This is a well known constellation which represents a woman sitting in a chair. It is a bright constellation lying in a rich part of the Milky Way, close to the celestial north pole and easily recognised by its large W.

It can be found on the opposite side of the Pole Star to the Great Bear (Ursa Major - The Plough or Big Dipper.) It contains two open clusters, M52 & M103 , of magnitudes 7.3 & 7.4 respectively. Cassiopeia is circumpolar, and is visible all year round in the Northern Hemisphere. Eta Cassiopeiae (star above the last letter "h" of Ruchbah) is a beautiful double star consisting of yellow and red components of 4th and 7th mags. NGC457, the Owl Cluster, is an attractive cluster for wide field telescopes, including 5th mag. white supergiant Phi Cassiopeiae. The stars of NGC457 are seemingly arranged in chains. Perseus Perseus looks likes an inverted Y and contains two of the most beautiful open clusters which sit side by side. NGC869 and NGC884 make up the famous Double Cluster, a related pair of star clusters that form one of the richest sights in the sky for small telescopes.

Each cluster covers more than 1/2 degree of sky, with NGC869 being the brighter and richer of the pair. NGC884, however has a beautiful sprinkling of red stars. Both clusters lie about 7400 light years away in a spiral arm of the Milky Way. Eta Persei (2nd star up from Mirfak) is an attractive double star consisting of orange and blue stars of 4th and 9th mags. in a star sprinkled field. Algol (beta Persei) is the prototype of the eclipsing binary variables. These consists of two stars in close orbit that periodically pass in front of each other as observed from Earth, causing a variability between mag. 2.1 and 3.4 every 2days and 21 hours. M34 is a large 5th mag. cluster, easily resolvable in small telescopes. We use cookies to improve our website and your experience when using it. Cookies used for the essential operation of the site have already been set. To find out more about the cookies we use and how to delete them, see our privacy policy . I accept cookies from this site.

Agree See the Demon Star Algol 'Wink' in the Night Sky See the Demon Star Algol 'Wink' in the Night Sky By Joe Rao, SPACE.com Skywatching Columnist | February 19, 2015 05:26pm ET MORE This sky map shows the location of Algol, the Demon Star, in the constellation Perseus in the western night sky on Feb. 19, 2015 as seen from mid-northern latitudes. Credit: Starry Night Software The so-called "demon star" of Algol is the most prominent eclipsing variable star in the night sky, and if you know when and where to look, you can see the star appear to wink as it is eclipsed by another, dimmer star. This variable star eclipse occurs like clockwork at intervals of 68 hours, 48 minutes and 59.9 seconds, or 2.86736 days. Because the entire eclipse takes 9 hours and 40 minutes from start to finish, the entire performance can be seen in a single night when the timing is right.

To find Algol in the night sky, you should look well up in the western sky at nightfall. Located near the W-shape of the constellation Cassiopeia is the constellation Perseus, which resembles a lopsided letter K in the sky. The lower arm of the K points at the Pleiades star cluster, but it upper arm ends at the star Algol, which has a long and venerable history. [ Star Quiz: A Stellar Challenge ] Coincidental moniker? The name Algol comes from the Arabic al-ghul, the female demon, but contrary to many popular accounts, the name apparently has nothing to do with the star's behavior. It is due merely to Algol's position marking the severed head of the Gorgon Medusa in ancient Greek constellation mythology. On the other hand, a 2013 paper published in the Astrophysical Journal by a team of researchers, suggests that a calendar for lucky and unlucky days composed in Egypt some 3,200 years ago, shows a distinct periodicity of 2.85 days and several empirical tests indicate that this periodicity just might be connected to Algol.

The literal translation of Algol means, "The Mischievous One." Yet if the dimming of Algol was noticed by the ancient watchers of the night sky , the records say nothing about it. Medusa winks Normally, Algol appears 3.3 times brighter than during the peak of the eclipse; it usually shines at magnitude 2.1, about equal to the nearby star Almach in the constellation Andromeda, but when it's at minimum light, it fades to about magnitude 3.3, or about equal to the brightest star in another nearby star pattern, Triangulum. While diminished light lasts nearly 10 hours, the eclipse begins and ends so gradually that most of the fading and subsequent brightening takes place within the two hours before and two hours after mid-eclipse. So the eye of Medusa seems to "wink" at nearly three day intervals. This table shows the times for mid-eclipse of Algol for North America. Credit: Starry Night Software First noticed 350 years ago The first person who definitely noticed Algol's winking behavior was the Italian professor of mathematics Geminiano Montanari of Bologna around the year 1667.

At that time the only other variable star known (save for a few novae) was Mira, whose light varies over months instead of hours. Perhaps this is why few other astronomers paid much attention to Montanari's discovery at the time. [ Top 10 Star Mysteries ] Algol's variability was rediscovered in 1782 by the English amateur astronomer John Goodricke, an 18-year-old deaf mute. He observed the star systematically and determined its period. Amazingly, he also correctly suggested the reason for the brightness variations: A large, dim body orbits the star and periodically blocks much of its light from our view. Here's how Algol's dimming nature works: The star is located about 90 light-years from Earth, and is actually made up of two stars in a binary system . The brighter star, Algol A is a bluish star about 90 times more luminous than our sun. The dimmer star Algol B is the eclipsing body. Algol B is a yellow star that is "dim" when compared to the brighter blue star, yet compared to our sun it is three times more luminous.

Algol A and Algol B are both several times larger than the sun. Yet another star, Algol C, circles the A and B pair from once every 1.86 years. Algol C is a white star that is four times as bright as the sun. The whole complex system is a source of radio and X-ray emission. Algol, the Demon Star, is located about 90 light-years away in the constellation Perseus, where it can be found as one of the eyes in Medusa's head as seen in Johannes Hevelius' Perseus illustration from Uranographia. Credit: Johanes Hevelius (Public Domain Image) How to see Algol's winking nature During the next month, Algol can be found about one-half to two-thirds up in the western sky as darkness falls. The star spends the rest of the night, slowly descending down into the northwest sky, and will be quite low to the northeast horizon by around 1 a.m. or 2 a.m. your local time. The table associated with this guide gives the dates and local times for the next four eclipses that can be observed from parts of North America in February and March.

Daylight Saving Time has been accounted for in March. When an asterisk (*) is used, it means that the eclipse will occur not on the date listed, but on the previous calendar day. "N.O." stands for "Not Observable," since the eclipse takes place too near to sunset and the sky will simply be too bright to see the star. Two hours before the predicted minimum start checking Algol's brightness. If you are observing casually, a look every half hour is sufficient; if you are trying to determine the time of mid-eclipse, 10-minute intervals are better. Algol is at minimum light for about 20 minutes — as the large, dim star passes across the smaller, brighter one — then it gradually returns to normal. Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmer's Almanac and other publications, and he is also an on-camera meteorologist for News 12 Westchester, N.Y. Follow us @Spacedotcom , Facebook and Google+ . Original article on Space.com . Constellations Constellations Constellations are useful because they help us find our way around the night sky.

There are 88 constellations which cover the entire sky. About 80 of them can be seen from Hawaii, but not all will be visible during the fall semester. We will study 10 or so of these constellations; most have brighter stars and are fairly easy to recognize. Background Reading: Stars & Planets, p. 5 to 10 (Constellations, Star names, and Star brightness). Additional readings for individual constellations are listed below. For thousands of years, people looking at the night sky have grouped stars into constellations. The stars making up a constellation often seem to trace recognizable patterns. For example, the stars in Orion outline a man wearing a sword, and the stars in Maui's Fish-hook follow the shape of a fishing hook. The stars making up a constellation usually have very little to do with each other; some may be relatively close, while others are much further away. But because stars move so slowly through space, the patterns we see today have hardly changed since the dawn of history. Some of the constellations we know today were first defined by our ancestors thousands of years ago.

The pattern of stars in the sky is basically random, much like the pattern made by spattering droplets of ink on a sheet of paper. If you look at a random pattern of dots for a while, your mind will start to group dots together, and some groups might even seem like pictures of things you know. Another person looking at the same pattern might come up with some of the same groups. It may surprise you to learn that professional astronomers don't use constellations to locate objects in the sky; instead, they use celestial coordinates . To point a modern observatory telescope at a particular object, you just give the object's celestial coordinates to a computer, and the machines do the rest. In this class we will use simple telescopes with manual controls, and a knowledge of the constellations will be helpful in finding things to observe. READING STAR-CHARTS It is fairly easy to recognize constellations using the sky charts in The Sky Tonight. These charts show how the sky actually appears from Hawaii at various times. Despite their circular shapes, these are not all-sky charts ; each shows a wide-angle view looking north, east, south, or west.

For example, chart 9-North shows the view looking north at about 20:30 (8:30 pm) in late September. The translucent overlay for each chart shows the outlines of the constellations and names some bright stars. Once you've found a constellation, turn to the individual constellation charts in Stars & Planets for more detail. These charts show every star you are likely to see with your naked eye. They label stars with Greek letters (and some with numbers). These Bayer letters (see Stars & Planets, p. 8) provide standard names for stars; for example, the bright star Vega is also called alpha Lyrae. You will need to be familiar with Bayer letters to locate the stars we discuss in this class. The charts in Stars & Planets also show the brightness of each star, using a system described below, and employ special symbols to indicate double and variable stars, star clusters, nebulae, and galaxies. APPARENT MAGNITUDES A star's apparent magnitude is a number which indicates how bright the star appears in the sky.

Bright stars have small apparent magnitudes, and faint stars have large apparent magnitudes; this may seem backward, but it made sense to astronomers thousands of years ago and we've been stuck with it ever since. The difference in the apparent magnitudes of two stars tells you the ratio of their brightnesses; a difference of 2.5 magnitudes implies a brightness ratio of 10:1. (Note: if you know about logarithms, you may recognize that the magnitude system employs a logarithmic scale.) To show what this means, suppose we have three stars, called A, B, and C: star A has apparent magnitude 1.0 mA = 1.0 star A appears 100 times brighter than star C mC - mA = 5.0 To give some specific examples, the three bright stars making up the ``Summer Triangle'' are Vega (magnitude 0.03), Altair (magnitude 0.76), and Deneb (magnitude 1.2). The brightest of these - that is, the one with the smallest magnitude - is Vega.

The constellation of Lyra, which includes Vega, is defined by several rather dim stars; the faintest is zeta Lyrae (magnitude 4.4). With the naked eye, the faintest stars visible from Kapiolani Park have apparent magnitudes of about 4.5, and the faintest stars visible from a really dark observing site have apparent magnitudes of 6.0 to 6.5. Knowledge of apparent magnitudes helps in planning observations. For example, you might want to know how much of the constellation of Cygnus will be visible. The five stars outlining the basic shape of this constellation have apparent magnitudes between 1.2 and 3.2; these are all easy to see. However, the chart for Cygnus in Stars & Planets (p. 135) incorporates several fainter stars with apparent magnitudes between 3.4 and 4.0; these will be harder to see unless you are looking from a fairly dark location. The constellation charts in Stars & Planets show stellar magnitudes by using dots of different sizes; in addition, magnitudes are usually included when individual stars are discussed in the text.

ANGULAR SEPARATIONS The angular separation of two objects is an angle measuring how far apart the objects appear from your point of view. For example, make a ``shaka'' with your arm outstretched, thumb up, and pinkie down; now imagine two lines extending from your eye to the tips of your thumb and pinkie, as shown in Fig. 1. These lines meet at an angle of about 20°, so the angular separation between the tip of your thumb and the tip of your pinkie is about 20° (this depends on the length of your arm and the size of your hand, but 20° is average). If two stars have an angular separation of 20°, you should be just about able to cover one with your thumb and the other with your pinkie by holding a shaka up to the sky at arm's length. Fig. 1. A ``handy'' measure of angular separation. At arm's length, the angle between your outstretched thumb and pinkie is about 20°. You can estimate smaller angles with your hand as well. For example, your fist, held at arm's length, defines an angle of about 10°.

A single finger, at arm's length, is about 2° wide. To measure angular separations more accurately, we will use a device called a cross-staff, which is basically a stick, 57.3 cm long, with a centimeter ruler mounted on one end. The length of the stick was deliberately chosen; if the ruler is 57.3 cm from your eye, 1 cm on the ruler defines an angle of 1°. (Note: if you know trigonometry, 57.3 = 1/tan(1°).) It's fairly easy to use a cross-staff; close one eye and place the end of the stick without the ruler just under the other eye. Sight along the stick towards the two stars you want to measure and adjust the markers on the ruler to line up with these stars. Finally, read off the positions of the markers on the ruler; the difference between them is the angular separation between the two stars. LEARNING CONSTELLATIONS It's often fairly easy to see a constellation when its pointed out in the sky, but harder to remember it so you can find it yourself.

The best way to really learn constellations is to draw them; when you do this, your eyes often find geometrical patterns which will help you identify these constellations later. You should make your drawings to scale; this will give you a feeling for the sizes of constellations. (Many people confuse the Pleiades with the Little Dipper, not realizing that one is about ten times the size of the other!) Here's how to make an accurate drawing: Identify the constellation in the sky; we will help you with this. Pick two bright stars in the constellation, and measure their angular separation. Plot those two stars on a sheet of sketch paper, using a scale of 0.5 cm per degree (unless you can't fit the constellation on the paper at this scale.) In the margin of your sketch, name the two stars you measured, and give the angle between them in degrees. Fill in the other stars, using the ones you've already plotted as reference points. Use larger dots to indicate the brighter stars. Try to show at least three levels of brightness (e.g., bright, faint, and dim). Note any stars with distinctive colors, and any other interesting observations (e.g., ``fuzzy'' stars).

Later, use a colored pencil to outline the shape of the constellation, and write the Bayer letter next to each star. Make sure to include your name, the name of the constellation, the date, and the time on your sketch. OBSERVING SCHEDULE Because different constellations are visible at different times, we will return to the study of constellations throughout the semester. p. 224 8-South Most of these constellations are easy to see; you may even know some of them. Cygnus and Sagittarius are bright constellations along the Milky Way. Sagittarius and Scorpius lie along the ecliptic. Lyra includes the star beta Lyrae, which is a famous variable star. p. 200 9-East Cassiopeia continues the sequence of bright constellations along the Milky Way. When observing Cepheus, note the star delta Cephei, which is the prototype of an important class of variable stars. Capricornus, although faint, lies along the ecliptic. The ``Great Square'' of Pegasus is useful signpost for the Autumn sky. p.

202 11-North Andromeda, although not very striking, contains the famous Andromeda Galaxy. Perseus lies along the Milky Way; it contains the variable star Algol (beta Persei). Star Lore of the Constellations: Perseus the Hero 15N 36N The constellation Perseus lies between Cassiopeia and the Pleiades. It is represented by Perseus holding a sword above his head in his right hand and the decapitated head of the gorgon Medusa in his left. On his feet are winged sandals, given to him as a gift from Mercury. The myth of Perseus tells how he was sent on a quest to bring back a gorgon's head to king Polydectes. The gorgons were three sisters, only one of whom, Medusa, was mortal. Originally a beautiful maiden, Medusa was transformed into a hideous monster by the goddess Minerva; a jealous and revenge-filled punishment for allowing herself to be seduced by Neptune in one of Minerva's temples.

Her hair was turned into a mass of poisonous snakes and her general appearance became so horrifying that anyone who looked upon her was petrified with terror. Perseus was able to cut off her head only by avoiding her direct gaze and monitoring her reflection in his shield. On his way back to Polydectes he rescued the princess Andromeda by petrifying the sea-monster (Cetus) with his revelation of Medusa's head. Although Manilius gives a detailed rendering of the myth of this constellation he neglects to describe its rising influence. Ptolemy lists the stars of Perseus as like Jupiter and Saturn, with the exception of 'the cluster in the hilt of the sword', which he describes as akin to the influence of Mars and Mercury. [1] This cluster is better known as Capulus - from a Roman term used to describe the richly engraved hilt of a sword. Al Biruni refers to it as one of the four most nebulous stars but dismisses the suggestion (frequently attached to nebulous clusters) that it causes blindness, arguing that vision is represented by the luminaries and this cluster is too high in latitude to fall on their path.

[2] Nonetheless Capulus continues to be related to a notion of blindness, (spiritual or emotional if not actually physical), reinforced by a myth where our hero is not able to look directly at the opponent that confronts him. Instead, the willingness to go on the offensive as suggested by the sword, (Mars), must be tempered by cunning or intellect, (Mercury); otherwise Capulus will suggest a passionate energy which dissipates or turns inwards through a lack of focus. As a whole, the constellation is said to give a bold, courageous and intelligent nature, but the group depicting the head of the gorgon is considered quite evil. Pliny and Hipparchus referred to this as a separate constellation and it was usual for the whole group to be referred to as 'Perseus and the Gorgon's Head'. The brightest star of the constellation is Mirfak, located in the side of the breast and therefore sometimes referred to as Algenib, Arabic for 'side'. This is a bright yellow-blue star, slightly less than 1st magnitude, and as the alpha star of the constellation embodies the principles of courage, and success through trials.

Ingenuity is also a hallmark of this constellation, and may be the reason why authors such as Robson and Noonan describe it as offering an adventurous nature but with a tendency to lie 'or be less than honest in their dealings with others'. Other important stars which share this reputation include Misam on the left arm, Miram on the right shoulder, Atik on the winged sandal of the left foot and Menkib, also on the left ankle. There is a clear distinction between the characteristics of the stars of Perseus and those of the Gorgon's Head, which Ptolemy fails to acknowledge in his list of planetary natures. Since most astrologers follow Ptolemy, Algol, (the main star in the Gorgon's head) is usually described as like Jupiter and Saturn in influence; but in view of its widespread and overwhelmingly malevolent reputation Lilly was probably more correct when he likened it to Saturn and Mars. [3] It is alleged to be the most unfortunate and dangerous star in the heavens and has a reputation for causing violence and unnatural death.

Even Ptolemy remarked upon its influence in bringing 'death by decapitation or mutilation', when tied into the hostile aspect of Mars to the Sun or Moon. [4] The name Algol comes from the Arabic Al Ghul, the 'Ghoul' or 'Demon'. Usually it is classed as a white star but it has also been listed as red. It seems, always, to have been connected with death, tragedy and bloody violence: the Hebrews knew it as Rosh ha Satan, 'Satan's Head', and the Chinese as Tseih She, 'Piled-up Corpses'. According to Dr Lomer in Kosmobiologie Arabic commanders ensured that no important battle began when the light of Algol was weak. [5] In ancient times it was referred to as 'the Winking Demon' or 'the blinking eye of the Gorgon', because it is one of the most variable stars in the northern sky, alternating its brilliance from 2nd to 3rd magnitude in a particularly notable fashion due to its short cycle of variability which completes in three days.

Most probably, its malefic reputation arose out of this variability, which threw a direct challenge to Aristotle's doctrine of the pure immutability of the heavens, by which celestial harmony was associated with perfect and constant motion. The inconstancy is caused by the fact that Algol is a binary system in which the brighter star is regularly eclipsed by its partner for a period of around 8 hours. Thus we get the ominous reference to an evil pulsating eye - a very powerful and provocative image and recently put to great effect by Tolkien as a representation of the evil Mordor in Lord of the Rings. [6] Lilly considered Algol to be one of the most portentous stars, noting its affliction as an indication of decapitation, hanging or danger to the head. In his system of scoring planetary strength, any planet within five degrees of Algol is detrimented by 4 points of debility. When placed with the Part of Fortune it threatens poverty or the loss of wealth, and with the 'significator of manners' it: "begets in the Native a certaine dogged nature and violence, whereby he either procures sudden death unto himself, or is the cause of it to others".

[7] Of the direction of the midheaven to this star Lilly writes: It perplexes and casts the Native into extreame danger by reason of Murder, Man-slaughter, or the sudden death of someone or other, the Native being either author or assistant, it endangers the Head: if other Directions concurre in good, it gives the Native power of putting others to death; but I ever found it an ill Direction, even in mean mens Genitures. [8] An astronomer whose name has become linked to Algol is John Goodricke, who in 1782 began the first scientific study of "variable stars" after having his attention caught by Algol and the way it had changed from bright to dim within a few hours. At the age of five Goodricke had contracted scarlet fever which left him totally deaf. He learned to lip-read to pursue his education, and made his discovery of Algol when he was just 18. He communicated his interest to his cousin Edward Pigott and throughout the following winter the two men measured Algol's brightness every evening.

Goodricke found that Algol's light changed every two days, 20 hours, and 45 minutes - within four minutes of the modern measure. It was Goodricke who theorized that Algol was really two stars, a bright star and a dim star, and that the two stars orbited each other in space. It would be 100 years before Goodricke's theory on binary stars would be proved correct, but the Royal Society recognised the value of his work and awarded him Britain's highest scientific medal, the Godfrey Copley Medal. He was later admitted into the membership of the Royal Society, but died of pneumonia (said to be after contracting a cold while observing in the cold night air) before hearing the news of this, on 20th April 1786. Both his deafness and the nature of his death are Saturn-ruled. Goodricke was born on 17th September 1764 with Saturn retrograde at 21° 35' Taurus, conjunct Algol then at 22° 53' Taurus. Algol brought him fame but it also brought him tragedy.

He was only 21 years old when he died. The best time to view Perseus is in the late autumn months. It appears as a distorted 'K' shaped constellation (some say giraffe shaped), located to the north of Taurus and the south of the easily identifiable 'w-shape' of Cassiopeia. The brightest star, Mirfak, lies north of Algol and on a line from Cassiopeia to Capella in the west. The Sun crosses Capulus around 15th May, Algol around 17th May, and Mirfak around 23rd May each year. Notes & References: Contrasting Star Colors in Perseus - EPOD - a service of USRA EPOD - a service of USRA The Earth Science Picture of the Day (EPOD) highlights the diverse processes and phenomena which shape our planet and our lives. EPOD will collect and archive photos, imagery, graphics, and artwork with short explanatory captions and links exemplifying features within the Earth system. The community is invited to contribute digital imagery, short captions and relevant links.

Contrasting Star Colors in Perseus August 05, 2012 Summary Author: Greg Parker A few years back, I took an image of the well known double star Albireo in the constellation of Cygnus , which has a close pair of blue and orange stars . In all the images I've taken since, I've never noticed such a color contrast in a pair of nearby, reasonably bright stars (there are actually an enormous number of much fainter red-blue close neighbors to be found). So I took a look at a star map to see if I could find any other colorful doubles to image that would fit into the field of view of my Takahashi Sky 90 refractor telescope . Surprisingly there was only one suitable pair of stars to fit the criteria -- Algol and Rho Persei in the constellation of Perseus . This would make an impressive pair of stars in a deep-sky image, and both are visible with the unaided eye, so they're pretty bright as well. In this image, Algol is the bright blue star and Rho Persei is the bright red star.

Algol (beta-Persei, SAO 38592) also known as the "Demon Star" is an eclipsing binary star , so an orbiting star eclipses Algol causing its magnitude to change from a relatively bright 2.1 to a much dimmer 3.4, every 2 days 20 hours and 49 minutes. Although Algol is an eclipsing binary, it's in fact a three-star system . Algol is 92 light years away, 98 times our Sun's luminosity , and has a surface temperature of 9,200 kelvin (K) . Color: appears blue-white. 25-Rho Persei (SAO 56138) is less commonly known as Gorgonea Tertia (the third of the four Gorgons ). Rho Persei is also a variable star ; it's a semiregular variable of the Mu Cephei type whose magnitude varies between 3.3 and 4.0 with periods of 50, 120 and 250 days.

Rho Persei is 325 light years away, 5 times as massive as the Sun, 150 times the Sun's radius, 2,290 times the Sun's luminosity, and has a surface temperature of 4,111 K. Color: the characteristic red-orange color of an M-type star. For comparison, our Sun has a surface temperature of 5,778 K, hotter than Rho Persei, so it appears more yellow than red, but much cooler than the blue-white Algol at 9,200 K. Later this week look toward Perseus in the northeastern sky (in the Northern Hemisphere) around midnight to see meteors from the annual Perseids Meteor shower . Since the Moon will be new when the Perseids peak (August 11-12), if skies are clear, you may be able to see 4 or 5 shooting stars per minute. Photo details: Takahashi Sky 90 telescope; M25C one-shot color camera (APS size chip). New Forest Observatory, U.K.

Coordinates: 50.819444, -1.59 Related Links Perseus Constellation - Facts About Perseus | Solarsystemquick.com Perseus Constellation Perseus is easily visible in the night sky due to the brightness of its stars. Perseus Constellation Facts Perseus is visible from August to March in the Northern hemisphere. It is visible in northerly areas of the Southern hemisphere from mid spring to early summer. Perseus is relatively bright and can be at least partially viewed even in well lit areas. The annual Perseids meteor shower emanates from the direction of the constellation. The Perseids occur from mid July to mid August, at times one meteor can be seen every minute. The shower happens as a result of Earth passing through a trail of debris left by the comet Swift-Tuttle. The Little Dumbbell and California nebulae are located within the Perseus constellation. Perseus is near several constellations whose names derive from the adventures of the Greek hero, known as the Perseus Group. Other constellations in the Perseus Group include Andromeda, Cassiopeia and Pegasus.

Perseus has been recognized as a constellation for at least 2,000 years. Perseus Mythology The Greek mythological hero Perseus holding the head of the gorgon Medusa. Perseus was a Greek mythological hero whose adventures provide the background stories of other constellations. He was fathered by the King of Gods Zeus who seduced his mother Danae, a beautiful princess whose father was the King of Argos. The King of Argos previously consulted an Oracle who predicted that his daughter’s son would eventually kill him. After Perseus was born the King therefore placed his daughter and newly born grandson into a wooden chest and sent them adrift into the sea. The pair survived and landed safely on an island, there they were taken in by a local nobleman who raised the young hero through his childhood. Once Perseus had reached adulthood the nobleman sent him on his most famous adventure, to slay Medusa, a snake haired Gorgon whose gaze could turn a man to stone. Perseus managed to cut off the monster’s head, avoiding her gaze with the aid of mirrors.

Perseus did eventually kill the King of Argos, striking him accidently in the head with a javelin at an athletic competition. Main Stars in the Perseus Constellation The number next to each star is its apparent magnitude, its brightness from our point of view on Earth, the lower the number the brighter the star in the night sky. Gamma With no traditional name the star is simply known as Gamma Persei, it's actually a binary system located around 240 light years from Earth, the primary star eclipses the other every 15 years causing it to appear dimmer in the night sky for a couple of weeks. Mirfak Also known as Alpha Persei, Mirfak is located around 500 light years from Earth and is the brightest star in the constellation, it's a white supergiant with a diameter around 30 times larger than the sun. Algol Also known as Beta Persei, Algol is actually a three star system located around 90 light years from Earth, the primary star is eclipsed by one of its less bright companions every 3 days causing its brightness to dip considerably for several hours.

In the late 18th century the star was the first such eclipsing binary to be discovered. Historically Algol has been referred to as the "Demon Star", this may be due to the ancients perceiving its dimming in brightness as a harbinger of bad luck. Gorgonea Tertia Also known as Rho Persei, Gorgonea Tertia is a red giant around 300 light years from Earth, it is 150 times larger in diameter than the sun. Epsilon Epsilon Persei is a binary or possible triple star system 640 light years from Earth, the primary star has surface temperatures 5 times hotter than the sun with a mass around 14 times greater. Zeta Zeta Persei is a blue supergiant around 750 light years from Earth, it is more than 25 times larger in diameter than the sun and almost 50,000 times as luminous. Finding Perseus - Northern Hemisphere The chart shows the position of Perseus over most of the United States in January at 8pm. This chart can also be applied to other areas of the Northern hemisphere such as Canada, the UK and Europe.

In August and September the constellation will first appear low on the north-eastern horizon around 11pm, gradually moving higher in the sky before appearing directly overhead before day break. In October and November Perseus will be visible low on the horizon in the north-east around 8pm, by 3am the constellation will be directly overhead before moving towards the north-western horizon. In December and January it will be visible in the eastern night sky at around 6pm, moving higher in the sky eventually reaching directly overhead at around 10pm, then reaching the north-western horizon before day break. In February and March the constellation will first appear overhead around 7pm, moving towards the north-western horizon as the night moves on. Finding Perseus - Southern Hemisphere The chart shows the position of Perseus over Northern Australia in December at 11pm. This chart can also be applied to more northerly areas of the Southern hemisphere. In Southern Australia and other southerly regions of the hemisphere Perseus is not visible. In November the constellation will appear low on the north-eastern horizon at around 10pm, gradually moving westwards and staying quite low on the horizon as the night moves on.

In December and January Perseus will be visible from around 10pm appearing low in the north-eastern or northern horizon, over the next few hours it will move westwards before dipping below the north-western horizon. Share this page

Question: In which constellation, visible from the UK is the bright star Algol to be found?
Answer: Perseus